The objectives of this research are: 1) to isolate and determine the structures of the pyrrolizidine alkaloids present in Heliotropium maris mortui, H. rotundifolium, H. arbainense, Trichodesma africanum, T. boissieri, Cynoglossum creticum, Crotalaria aegyptiaca, Senecio flavas, S. jopensis, and S. vernalis; 2) to evaluate the carcinogenic activity of these plant extracts and isolated alkaloids in collaboration with Dr. R. Schoental of the Royal Veterinary College, University of London; 3) to attempt to present a unifying hypothesis for the mode of action of these chemical carcinogens in collaboration with Dr. Schoental. The plants will be collected by Dr. A. Danin, plant taxonomist-ecologist of the Hebrew University of Jerusalem, extracted under the direction of Professor A. Shani of the Ben-Gurion University of the Negev, Beer-Sheva and the alkaloids separated and their structures determined in our laboratories at the School of Chemistry, Georgia Institute of Technology, using single crystal X-ray analysis (under the direction of Professor J. Aaron Bertrand), nuclear magnetic (H1 and C13) and mass spectrometry in addition to the classical methods.